Demetallization process using ironcontaining catalysts

ABSTRACT

A PROCESS FOR THE DEMETALLIZATION OF HYDROCARBONS BY CONTACTING WITH AN IRON-CONTAINING CATALYST UNDER HYDROGENATION CONDITIONS.

United States Patent US. 'Cl. 208-451 H 3 Claims ABSTRACT on THEnrscLosUiiE A process for the demetallization of hydrocarbons bycontacting with an iron-containing catalyst under hydrogenationconditions.

Our invention relates to a process for the demetallization ofhydrocarbon stocks containing undesirable quantities of metalliferouscontaminants. More particularly, our invention relates to the removal ofmetals such as nickel and vanadium from hydrocarbon stocks by contactingthe stock with an iron-containing catalyst and hydrogen underhydrogenating conditions.

A Wide variety of liquid hydrocarbon stocks such as crude petroleum oil,shale oil and synthetic crudes derived from coal or tar sands, are knownto contain trace amounts of metals. Usually, these metals are part ofthe heavier, higher boiling, more complex, molecules present in thehydrocarbon stocks and while, at times, small amounts can be toleratedin a feed stock, the presence of any significant quantity of metals canresult in an undesirable high metals content in products and/or can present a problem in the catalytic processing of stocks containing theheavier molecules. What actually constitutes a significant quantity ofmetals can, of course, vary depending upon the processing to which thestock is to be subjected. Thus, for example, in the hydrodesulfurizationof residual containing stocks or synethic crudes, a comparatively highmetals level can be tolerated relative to the requirements of many otherprocesses; however, it is still desirable to reduce the metals contentof such stocks, usually greater than about 50 p.p.m., to a level of lessthan about 50 p.p.m., e.g. less than about 35 p.p.m. and

preferably less than about 25 p.p.m. On the other hand,

the presence of comparatively small concentrations of metals, e.g.p.p.m., in a stock to be subjected to eatalytic cracking is undesiredand the metals content of such stock should be reduced to less thanabout 1 p.p.m.

In connection with the catalytic processing of stocks comprising heaviercomponents containing metalliferous contaminants, the usual result isthat the metals deposit on the surface of the catalyst resulting indeactivation of the catalyst. While it is known in the art to removecarbonaceous deposits from catalysts by an oxidative burnoff technique,such procedure is apparently ineffective for the removal of metalsdeposited from the feed stock and, accordingly, metals poisonedcatalysts generally are not regenerable employing simple, art-recognizedtechniques. Thus, for example, in a fluidized bed operation, such as,fluidized catalytic cracking, wherein a portion of the catalyst iscontinuously withdrawn, subjected to an oxidative burn-otf, and thenreturned to the reactor, the life of the catalyst, in the absence ofmetals poisoning, is theoretically indefinite and practically quiteextensive. When treating a hydrocarbon stock containing metalliferouscontaminants, however, such operation, While removing carbon, does notremove any of the metals deposited on the catalyst surface and themetals poisoning is irreversible and cumulative thus providing anextremely short life for the catalyst.

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Another problem is presented by the hydrocarbon stock having anextremely high metals content, for example, greater than about or 100p.p.m. nickel plus vanadium, but having a comparatively low yet stillundesirably high sulfur content, for example, about 1.5 to 2% by weightsulfur. In the treatment of such stocks by traditional techniques forthe removal of sulfur, a lesser overall reduction of sulfur or a lesserpercentage of sulfur removal is practiced resulting in a reduction inthe quantity of metals removed thereby producing a product stillcontaining a high concentration of metals. Such desulfurized material isgenerally not a desirable feed stock to another catalytic process orsuitable as an end product per se.

It will be seen, therefore, that a need still exists in the art for aconvenient means of reducing the metals content of hydrocarbons prior tovarious catalytic treatments and to avoid producing high metals contentproducts. This is particularly so in dealing with high metals contentand comparatively low sulfur content stocks wherein a high proportion ofdemetallization is required together with only a moderate degree ofdesulfurization.

In recent years, the problem confronting the art has been the reductionof comparatively high sulfur content (e.g. about 4%) and comparativelylow metals content stocks (e.g. less than about or p.p.m.) to productscontaining about 1% by weight sulfur or less. To accomplish thisdesirable goal, it has been found that some traditional desulfurizationcatalysts, when employed under specific conditions, were effective toreduce the sulfur content of the high sulfur feed stocks without anundesirably high degree of metals removal. More recently, improvedcatalysts and improved processes have been developed whereby increaseddesulfurization could be effected with decreased metals removal therebyextending catalyst life in such situations. The process of our inventionis not directed to such an operation, but rather is directed to thereverse situation of removing substantial quantities of metals withoutremoving substantial quantities of sulfur.

As a means of evaluating or characterizing catalysts, we employ an indexor ratio indicating metals removal relative to sulfur removalrepresented by the expression AM/AS wherein AM is the percent by weightreduction of metals content, i.e. nickel plus vanadium, of the materialtreated while AS is the percent by weight sulfur reduction. Generally,catalysts suitable for employment in desulfurization, particularly indesulfurization of comparatively high sulfur content stocks, will befound to have an index of AM/AS of less than about 1.15 and preferablyless than about 1.10 With certain exceptional catalysts having an indexbelow about 0.75. As distinguished from such prior art catalysts, thematerials we employ have an index of AM/AS of at least about 1.20 andpreferably greater than about 1.25.

In accordance with our invention, we contact a hydrocarbon stockcontaining metalliferous contaminants with hydrogen and aniron-containing catalyst under hydrogenating conditions of elevatedtemperature and pressure. The catalyst employed in our process containsat least about 1% by weight iron based upon the total catalyst.

The feed stocks suitable for employment in our process comprise anyhydrocarbon stock containing a significant or undesired quantity ofmetalliferous contaminants. Usually, such feed stocks will be found tobe those containing the heavier higher boiling components, such as theresidual components of crude petroleum oil. Thus, generally, our processis suitable, for example, for the treatment of any petroleum stockboiling above about 300 F. and particularly stocks containing residualcomponents.

Illustrative of such materials are full crudes, topped crudes, reducedcrudes, atmospheric tower bottoms, vacuum tower bottoms and fractionsthereof whether subject to prior treatment or not. More specifically,suitable feed stocks to our process are stocks to be treated fordemetallization prior to catalytic processing such as charge stocks tohydrodesulfurization processes (particularly residual stocks) or chargestocks to catalytic cracking processes, including previouslydesulfurized charge stocks. Also, our process is particularly suitablefor the treatment of comparatively high metals content 70 p.p.m.) andlow sulfur content 2%) crude oils, such as Venezuelan crudes.

As mentioned above, the catalyst employed in our process contains atleast about 1% by weight iron as the metal and can be comprised of up to100% iron oxide. Advantageously, the catalyst of our process will alsocontain a metalliferous hydrogenating component, such as, for example,the Group VI and Group VIII metals, their oxides and sulfides eitheralone or in combination. The hydrogenating component is believed to beeffective in the prevention of coke formation on the surface of thecatalyst thereby extending its cycle life. Usually, the hydrogenatingcomponent is distended on the surface of a carrier such as any of thehigh surface area materials well known in the art including, forexample, the refractory metal oxides. The iron component of the catalystemployed in our process, when employed in conjunction with ahydrogenating component, however, can be present either as a portion ofthe carrier itself or distended on the surface of a carrier in the samemanner as a hydrogenating component. Thus, for example, iron and anotherGroup VIII metal of a Group VI metal can be distended on a carrier suchas alumina in order to provide a satisfactory catalyst for our process.Alternatively, the iron component can be present in the carrier for aGroup VI or Group VIII metal hydrogenating component. In such case thecarrier can be iron oxide, a mixture of iron oxide and a wellknowncatalyst support such as silica, a complex metal oxide such as aniron-containing spinel (e.g. iron silicate), or, preferably, aninorganic polymer of iron, silicon and oxygen obtained by cogelling asilica sol and an aqueous solution of an iron salt of the type describedin U.S. Pat. No. 3,551,352.

The operating conditions employed in the process of our inventioncomprise a temperature in the range from about 600 to about 1,000 F.,preferably from about 650 to 900 F.; a pressure from about 500 to about5,000 p.s.i.g., preferably from about 750 to 2,000 p.s.i.g.; a liquidhourly space velocity (LI-ISV) from about 0.1 to about 10 volumes offeed stock per volume of catalyst per hour, perferably from about 0.5 to5 v./v./hr.; and a hydrogen feed rate in the range from about 500 toabout 10,000 standard cubic feet per barrel (s.c.f./b.), preferably fromabout 2,000 to 8,000 standard cubic feet per barrel.

In order to illustrate our invention in greater detail, reference ismade to the following examples.

EXAMPLE 1 In this example, three separate runs were conducted employinga 50% reduced Kuwait crude containing nominally 4% by weight sulfur asthe feed stock. The operating conditions employed in all runs were atemperature of 700 F., a pressure of 1,000 p.s.i.g., an LHSV of 1 and ahydrogen feed rate of 5,000 s.c.f./b. In the first run, a commerciallyavailable catalyst containing 0.5% by weight nickel, 1% by weight cobaltand 8% by weight molybenum supported on an alumina carrier was employed.In the second run, the catalyst contained the same hydrogenating metalsin the same proportions but the carrier employed was an experimentalsupport comprised of an intimate mixture of two different aluminasobtained by calcining a mixture of an alumina trihydrate and an aluminahydrate containing from 1.2 to 2.6

4 L rnols of water of hydration per mol of A1 0 The third run wasconducted employing a catalyst containing the same hydrogenating metalsin the same proportions as in the other two runs but employing a carriercomprising an inorganic polymer of iron, silicon and oxygen obtained bycogelling a silica solution and an aqueous solution of ferric chlorideand then calcining the gel. This carrier contained about 17% by weightiron.based upon the carrier or about 15% by Weight based upon the totalcatalyst.

The feed stock and product inspections for the three runs of thisexample are shown in Table I below. The results shown were obtainedbetween 40 and 48 hours for the commercial and experimental aluminas andbetween 32 and 40 hours for the polymer carrier.

From the above data it will be seen that the process of our inventionwas effective to remove a substantial quantity of metals from the feedstock. Further, it will be noted that the index, AM/AS, indicates thatsuch metals removal was accomplished with a comparatively low sulfurremoval. Thus, the catalyst support on the commercial alurnina had anindex of 1.03 and the catalyst support in the experimental alumina (acatalyst specifically designed for high sulfur removal with low metalsremoval) had an index of only 0.57, while the catalyst required by ourinvention had the extremely high index of 1.48. Further, it will benoted that these varying results were obtained under identical operatingconditions with catalysts having identical hydrogenating components.

EXAMPLE 2 In this example three separate runs were also conductedemploying a 50% reduced Kuwait crude containing nominally 4% by weightsulfur as the feed stock. Again, the operating conditions employed inall runs were a temperature of 700 F., a pressure of 1,000 p.s.i.g., anLHSV of 1 and a hydrogen feed rate of 5,000 s.cf./b. In all of the runsof this example the catalyst carrier was the same commercial aluminaemployed in Example 1 and there were deposited on the carriers threemetallic components. In all of the catalysts two of the components were8% by weight molybdenum and 5% by weight titanium. The three catalystsdiffered, however, in that each one contained 3% by weight of adifferent iron group metal (i.e. iron, cobalt and nickel).

The feed stock and product inspections for the three runs of thisexample are shown in Table II below. The results shown were obtainedbetween 40 and 48 hours on stream.

From the above data it will be seen that the catalyst required by ourinvention provides a comparatively high dernetallization for the amountof sulfur removed as shown by the index of 1.67 compared with theindices of 1.09 and 0.96 obtained with the other catalysts. Furthermore,it will be noted that the operating conditions in all runs wereidentical and that the catalysts differed, one

from the other, only in the presence of the different iron group metals,thereby demonstrating that the characteristic of demetallization ispossessed only by iron and not by the other iron group metals.

We claim:

1. A process for the demetallization of hydrocarbon stocks whichcomprises contacting the stock containing metals with hydrogen and acatalyst at a temperature in the range of from about 600 to about 1000F. and a pressure in the range from about 500 to about 5000 p.s.i.g.,said catalyst comprising at least one hydrogenating metal selected fromthe Group VI and Group VIII metals composited with a support containingiron, the concentration of iron being at least 1.0% by weight of saidcatalyst.

2. The process of Claim 1 wherein said hydrogenating metals comprisenickel, cobalt and molybdenum.

3. A process for the demetallization of hydrocarbon stocks containingsulfur which comprises contacting a stock containing metals and sulfurwith hydrogen and a catalyst at a temperature in the range of from about600 References Cited UNITED STATES PATENTS 3,271,302 9/1966 Gleim 2082643,496,099 2/1970 Bridge 208251 H 3,573,201 3/1971 Annesser et al. 2082533,551,352 12/1970 Carr et al. 252439 DELBERT E. GANTZ, Primary ExaminerJ. M. NELSON, Assistant Examiner US. Cl. X.R. 208253

